Electric water heating elements are normally connected to the wall of a water tank and are well grounded to earth because the tank is well grounded by reason of its water pipe connections.
We have discovered that many types of water heating elements are susceptable to damage by surges of high voltage, such as may be caused by lightning disturbances. Such surges may cause a puncture in the sheath of the heating element which eventually causes the end seal in the sheath to leak, whereby water from the tanks leaks outwardly of the sheath to the area adjacent to the tank to cause water damage and resultant liability claims.
To minimize the probability of sheath puncture, and consequent damage, we incorporate a spark gap into the present heater design which will harmlessly shunt high voltage surges to ground, and thereby limit the level of overvoltage impressed on the electrical insulation inside the sheathed heater. Our invention provides this overvoltage protection without materially increasing the cost of manufacture of presently known electric water heater constructions.